While a camera is often a good idea for fragile documents and old photographs, because of various optical aberrations associated with camera lenses, cameras are not necessarily a good idea for geospatial documents, where distortions can put landscape features in incorrect places. This problem is compounded if adequate reference sites no longer exist for georeferencing. To capture raw raster images of the maps, there are a number of different options including 1) physically dividing the original maps into scannable portions and merging in software (cheapest, fastest, but you lose the integrety of the original documents - not a big deal if they are almost lost already - huge deal if the existence of the physical maps themselves is of particular importance (e.g. official treaty boundary maps). ; 2) Heads-down hand digitization using a tablet and stylus (takes a long time, pain in the rear, results in vector equivalent to map); 3) hire out to a shop with large format scanner (print shops, newspaper offices, even city offices may provide these services if you ask) - University geography departments are often interested in unique problems like this - might even do the rubbersheet georeferencing for you for free.
